Apparatus for supplying multiple burners with fine-grained fuel

ABSTRACT

With an apparatus for supplying multiple burners with fine-grained fuel from a storage container, with thermal conversion of solid fuels in a gasification reactor, wherein the storage container is equipped with a discharge cone, a solution is supposed to be created with which the required excess gas amounts can be reduced and it is possible to do without separate discharge cones per burner line, without giving up the uncoupling of the burner lines. 
     This is achieved in that the discharge cone ( 1 ) is equipped, at least in certain regions, with a gas-permeable wall region ( 6, 6 ′) and with at least two solids discharge lines ( 15 ) that lead to the burners.

The invention is directed at an apparatus for supplying multiple burners with fine-grained fuel, of the type indicated in the preamble of claim 1.

In the thermal conversion of solid fuels, such as, for example, different coals, peat, hydrogenation residues, waste materials, garbage, biomasses, and flue dust, or a mixture of the stated substances, under elevated pressure, there is the need to bring the substances used, which are stored under normal pressure and ambient conditions, to the pressure level of the thermal conversion, in order to allow conveyance into the pressurized reactor. Possible thermal methods can be, for example, combustion under pressure or gasification under pressure, according to the fluidized bed method or entrained flow method.

Metering of fine-grained fuel from a storage container for transport to the burners is a prerequisite for optimal gasifier operation.

One possibility of metering consists in that the storage container is fluidized, similar to a fluidized bed (EP 0 626 196 A1/DE 41 08 048 A1). This variant has the disadvantage that for one thing, greater amounts of gas are required for fluidization, and, for another, the pressure at the exit in the conveying pipe is sensitively determined by the properties of the fluidized bed. The fluidization state and the fluidized bed height have a direct effect on the exit pressure. If non-homogeneous, in other words bubble-forming fluidization is involved, pressure/density fluctuations additionally occur, which influence the exit pressure and thereby the exit mass stream.

Another possibility of allowing solids discharge from a container consists in providing conical run-out geometries, taking the bulk material properties into consideration. Solids run-out from a cone can be supported by means of adding gas by way of or at the cone walls (US 2006/0013660, U.S. Pat. No. 4,941,779), whereby gas is supplied to the discharge cone by way of porous elements. The amount of gas is generally smaller than the amount that would be required for fluidization, but sufficient to eliminate the wall friction of the bulk material and/or to prevent local deposits leading to bridge formation. In this connection, as described, the solid is drawn off from a bulk material layer (DE 10 2008 012 731 A1, DE 10 2008 014 475 A1). By means of adding gas into the conveying line or the container cone run-out directly at the beginning of the conveying line, an attempt is made to adjust a solids stream density that is as constant as possible.

The latter method is the preferred variant in the gasification systems described, in which fine-grained fuel must be handled both under atmospheric pressure and under high pressure. In this connection the required gas amount is limited, in contrast to full fluidization, and, at the same time, it is possible to do without mechanical installations.

In the case of great systems power, a separate discharge cone is generally provided for each burner line. In the case of great solids withdrawal streams, the amount of gas to be supplied to ensure discharge by way of the cone is clearly lower than the amount of gas added to adjust the conveying density in the dense stream, i.e. gas must be added to the solid below the cone, for example, for further dense stream conveying. Furthermore, additional gas is generally required in the container to maintain the pressure.

It is the task of the invention to reduce the required excess gas amounts and to be able to do without separate discharge cones per burner line, without giving up the uncoupling of the burner lines.

This task is accomplished, according to the invention, with an apparatus of the type indicated initially, by means of the characterizing characteristics of claim 1.

It is evident that loosening of the fine-grained fuel to be conveyed is positively influenced by means of the gas-permeable wall regions of the discharge cone, whereby at the same time, multiple solids lines that lead to the burners, in each instance, can be charged with fuel.

Embodiments of the invention are evident from the dependent claims. In this connection, it can particularly be provided that the solids discharge lines in the cone are provided below the gas-permeable wall surfaces in the direction of gravity. By means of this measure, it is guaranteed that each of the burner lines can be charged with correspondingly loosened fuel.

The configuration of the cone wall can be carried out very differently. One of the apparatuses according to the invention consists in that the gas-permeable wall surfaces in total form the wall surface of an element of the discharge cone shaped as a truncated cone.

In order to guarantee better installation and, if applicable, better replaceability if damage occurs, the invention also provides that the discharge cone is formed from multiple elements, connected with one another, particularly elements shaped as truncated cones.

It has proven to be practical if, as the invention also provides, the cone is provided with a closure bottom that is gas-permeable at least in certain regions.

In a further embodiment, it can be provided, according to the invention, that a double-walled element shaped as a truncated cone is directly assigned to the storage container for the fine-grained fuel, with a gas-permeable inner wall made of a sintered metal, a perforated metal sheet or the like, whereby such a design, in itself, is known for a total cone from the document US 2006/0013660 mentioned above.

In order to also facilitate and optimize the solids discharge, it can also be provided, according to the invention, that the solids discharge lines have an angle less than 90° relative to the vertical axis of the cone, directed downward in the direction of gravity, whereby a possibility of such a configuration can consist in that the solids discharge lines are positioned at a right angle to the related cone wall.

Depending on the fuel, it can be practical if an inner stirring device is assigned to the closure bottom. Such an inner stirring device has a number of advantages. It can serve to support fluidization by means of mechanical loosening, can allow uniformization of the fluidized or loosened solids density, and can bring about a reduction in the bubbles that can occur in the case of fluid gas feed.

In a further embodiment, it is provided, according to the invention, that the closure bottom and/or the lower region of the discharge cone, in the direction of gravity, is provided with media feed lines, particularly for loosening the solid in the cone interior. With this embodiment, it is possible to also meter additives into the actual fuel, for example substances that influence the ash melt behavior, for example mineral, organic substances, but also ashes, slag or the like, whereby the slag can be recirculated.

Further details, characteristics, and advantages of the invention are evident on the basis of the following description and using the drawing. This shows, in

FIG. 1 a fundamental sectional representation through a discharge cone according to the invention,

FIGS. 2 and 3 top views, according to Arrow II/III in FIG. 1, of two embodiment variants of the discharge cone, and in

FIGS. 4 and 5 in the representation of FIG. 1, two variants of the discharge cone configuration.

The discharge cone 1 shown in FIG. 1 is divided into segments, which is advantageous from the aspect of production technology, and consists of an inner cone 2 that forms the fluidization region, the solids discharge region 3, and the cone bottom 4. The discharge cone can also be structured, according to the invention, as a component (not shown here) that has the properties according to the invention.

The fluidization region is formed by a pressure-resistant outer mantle 5, the inner cone 2 that lies within it, the fluidization means feed 7, and the two connection flanges 8 a and 8 b.

The discharge cone 1 is connected with a solids container, not shown in the figures, by way of the connection flange 8 a. The wall of the inner cone 2 is structured as a permeable wall region 6 for the fluidization means, and the opening angle relative to the vertical or to the direction of gravity (arrow “g”) is described by the angle α₁.

The fluidization means (arrow 9) that flows through the fluidization means feed 7 distributes itself in the fluidization means distribution space 10 formed between the outer mantle 5 and the inner cone 2. From there, it flows through correspondingly gas-permeable regions of the inner cone 2. The solid (arrow 11) that enters into the discharge cone 1 from above, with gravity, is loosened at the inner cone 6 by the supplied fluidization means and flows into the solids discharge region 3 that follows below the fluidization means region 2.

The solids discharge region 3 consists of the two connection flanges 12 and 13, the cone wall 14 with the opening angle α₂ relative to the vertical, and the solids discharge lines 15. The solids discharge region 3 is connected with the discharge flange 8 b of the fluidization region of the discharge cone 1 by way of the connection flange 12. The loosened solid enters into the solids discharge region 3 and is drawn off by way of the two solids discharge lines 15 shown in this exemplary embodiment of FIG. 1.

The opening angles α₁ and α₂ of the cone walls, in each instance, can be of different sizes, for example in order to vary the construction height of the discharge cone 1.

The solids discharge region 3 is connected with the connection flange 16 of the cone bottom 4 by way of the connection flange 13. The cone bottom 4 possesses an additional fluidization means feed 17. The fluidization means (arrow 9 a) can be introduced into the solids discharge region 3 by means of a gas distribution apparatus 18 of the cone bottom 4. The gas distribution apparatus 18 is advantageously represented, in FIG. 1, as a centrally disposed nozzle, whereby bridges or blockages are loosened up and the density of the gas/solid mixture to be conveyed can be adjusted to the desired range.

The gas distribution apparatus 18 can also be configured, for example, as one or more porous elements in the bottom, as a perforated distributor, or as a multiple nozzle arrangement. Which of the variants is to be used is decisively determined, in an individual case, by the bulk material properties of the solid to be conveyed.

FIG. 2 shows a schematic top view of an exemplary embodiment of the invention, with three exits for the solids discharge lines 15, the gas distribution apparatus 18 disposed centrally in the bottom, and the inner cone 6, which is configured entirely from a material that is permeable for the fluidization means, in this example. The discharge cone 1 is fixed in place on the container run-out by way of screw connections, by way of the connection flange 8 a.

FIG. 3, just like FIG. 2, shows a schematic top view of an exemplary embodiment of the invention, with the difference that the inner cone 6′ is equipped only in certain segments with material that is permeable for the fluidization means. If the bulk material properties of the material to be conveyed permit this, the amount of gas to be supplied by means of the reduced permeable surface can be further reduced.

In an advantageous embodiment, the non-permeable regions of the inner cone 6 are produced from steel or stainless steel, and connected with the permeable surfaces, which consist of sintered metal, by means of welds, for example. In this connection, the fluidization regions disposed in segments are preferably disposed directly above the outlets of the solids discharge lines 15, in order to guarantee stable solids feed.

Furthermore, in this advantageous arrangement, a fluidized region lies opposite a non-fluidized region, in each instance, so that the risk of blockage due to bridge formation can be minimized. In this way, by means of configuring segments of the inner cone 6 from material not permeable for fluidization means, the gas consumption can be further reduced, without endangering the discharge.

In FIGS. 4 and 5, two variants of the apparatus according to the invention are shown, whereby the functionally equivalent elements bear the same reference numbers.

In a modification of the exemplary embodiment according to FIGS. 1 to 3, FIG. 4 additionally shows a stirrer 19 in the solids discharge region 3′, the drive shaft 20 of which is passed through a flange bottom 22, which is fixed in place on the flange 13, by way of a shaft seal 21. In addition, gas feeds 23 are provided, which can be equipped with a nozzle 24, for example, in order to guarantee optimal gas distribution. However, this nozzle can also be structured by way of an open pipe as a typical fluidized bed bell nozzle, or as a porous material.

In FIG. 5, a variant is shown in which an additive can be metered in, for example, for which purpose the solids discharge region 3 is provided with a solids feed connector 25. The solids feed is indicated by an arrow 26. The feed of the solid can be promoted if the feed is disposed, as shown in FIG. 5, in the region of the stirrer 19.

Of course, the exemplary embodiments of the invention as described can still be modified in many different aspects, without departing from the basic idea. For example, not only the solids discharge lines 15 but also the solids introduction line 25 can be positioned at different locations and in different numbers; depending on the design, the gas feed connectors can also be configured to be double-walled, in order to supply solids centrally and gases on the outer wall side, and more of the like.

REFERENCE SYMBOL LIST

1 discharge cone

2 fluidization region

3 solids discharge region

4 cone bottom

5 outer mantle

6, 6′ gas-permeable wall region (inner cone)

7 fluidization means feed

8 a, 8 b connection flange

9, 9 a arrow

10 fluidization means distribution space

11 arrow

12 connection flange

13 connection flange

14 cone wall

15 solids discharge line

16 connection flange

17 fluidization means feed

18 gas distribution apparatus

19 stirrer

20 distribution shaft

21 shaft seal

22 closure bottom

23 gas feed

24 nozzle

25 solids feed line

26 arrow

“g” directions of gravity 

1. Apparatus for supplying multiple burners with fine-grained fuel from a storage container, with thermal conversion of solid fuels in a gasification reactor, wherein the storage container is equipped with a discharge cone, wherein the discharge cone (1) is equipped, at least in certain regions, with a gas-permeable wall region (6, 6′) and with at least two solids discharge lines (15) that lead to the burners.
 2. Apparatus according to claim 1, wherein the solids discharge lines (15) are provided in the cone (1), below the gas-permeable wall regions (6) in the direction of gravity.
 3. Apparatus according to claim 1, wherein the gas-permeable wall regions (6) in total form the wall surface of an element (2) of the discharge cone (1) shaped as a truncated cone.
 4. Apparatus according to claim 1, wherein the discharge cone (1) is formed from multiple elements (2, 3, 4), particularly elements shaped as truncated cones, which are connected with one another.
 5. Apparatus according to claim 4, wherein the discharge cone (1) is provided with a closure bottom (4), which is gas-permeable at least in certain regions.
 6. Apparatus according to claim 1, wherein a double-walled element shaped as a truncated cone, having a gas-permeable wall region (6) made from a sintered metal, a perforated metal sheet, or the like, is directly assigned to the storage container for the fine-grained fuel.
 7. Apparatus according to claim 1, wherein the solids discharge lines (15) are disposed on the cone at an angle less than 90° relative to the vertical axis, directed downward in the direction of gravity.
 8. Apparatus according to claim 7, wherein the solids discharge lines (15) are positioned at a right angle relative to the related cone wall (14).
 9. Apparatus according to claim 1, wherein the closure bottom (22) has an inner stirring device (19) assigned to it.
 10. Apparatus according to claim 1, wherein the closure bottom (22) and/or the lower region of the discharge cone (1), in the direction of gravity (g), is provided with media feed lines (23, 25), particularly for loosening the solid in the cone interior or for applying additives. 